(function (doc, win) {
    var docEl = doc.documentElement,
            resizeEvt = 'orientationchange' in window ? 'orientationchange' : 'resize',
            recalc = function () {
                var clientWidth = docEl.clientWidth;
                if (!clientWidth)
                    return;
                if (clientWidth >= 640) {
                    docEl.style.fontSize = 200 + 'px';
                } else {
                    docEl.style.fontSize = 100 * (clientWidth / 320) + 'px';
                }
            };
    if (!doc.addEventListener)
        return;
    win.addEventListener(resizeEvt, recalc, false);
    doc.addEventListener('DOMContentLoaded', recalc, false);
})(document, window);

